Proper Serving Temps?

I just read a post about someone's first brew, and someone recommended serving at 41 from a room temp glass, which is interesting.

Having tackled a first (and slightly young 3 weeks primary/1 week bottled) beer this last weekend (I know, wait three weeks in bottle- I set half aside as off limits), we noted that it was actually tastier warm, unlike a BMC which starts at crappy and gets worse as it gets warmer.

What's the theory/ rules of thumb on this? IE does it vary with styles, etc?

it definitely varies with style but it also varies with personal taste. here's a little something to get you started thinking about it: http://www.realbeer.com/library/beerbreak/archives/beerbreak20000921.php

Basically, the colder a beer is, the less your tastebuds are able sense it. That's why bars will serve BMCs in frosty mugs, so it's nice and refreshing and tasteless. Now, that's not to say you should drink all of your beer at room temperature (unless you're English... Ba-zing!). If you look at android's link above you'll see that, generally speaking, the more flavourful and complex the beer (i.e. nice, heavy stouts) the warmer you want to drink it.